1. Field of the Invention
The present invention relates to a driving apparatus utilizing a motor as a driving source, for particular use in an optical apparatus, for example.
2. Related Background Art
Hitherto, an apparatus shown in FIG. 9 was known as a lens driving apparatus for a still camera, a video camera, and the like. Referring to FIG. 9, a lead screw 102 is connected to the output shaft (not shown) of a step motor 101. A frame 103 rotatably holds the ends of the lead screw 102 and fixes or secures the step motor 101 as well. The frame 103 is fixed to a bottom board (not shown).
A lens frame 105 has an arm portion, including an internal thread engaged with the lead screw 102. The lens frame 105 fixes or holds a lens 104. Also, the lens frame 105 can move in the direction of the optical axis of the lens, while rotation about the lens optical axis is restricted by a bottom board (not shown).
In a lens driving apparatus constructed as discussed above, when the lead screw 102 is rotated by the step motor 101, the lens frame 105, which is engaged with the lead screw 102 at the internal screw portion, is moved. Consequently, the lens 104 is moved in the back and forth directions of the optical axis, corresponding to the revolution of the step motor 101. By this back and force motion, focusing, zooming, etc., can be achieved.
A conventional step motor is shown in FIG. 10. A stator coil 115 is concentrically wound around a bobbin 111. The bobbin 111 is clamped between two stator yokes 116 in the axial direction. In the stator yokes 116, stator teeth 116a and 116b are alternately disposed in the circumferential direction of the internal radius of the bobbin 111.
The stator yoke 116 is integrally fixed, in a case 113a or 113b, with the stator teeth 116a or the stator teeth 116b. Thus, the stator 112 includes the bobbin 111, the stator coil 115, and stator yoke 116.
A flange 125 and a bearing 118a are fixed to the case 113a, while a second bearing 118b is fixed to another case 113b. A rotor 119 has a rotor shaft (output shaft) 120 and rotor magnets 121, fixed to the rotor shaft 120. Gaps are radially formed between the rotor magnets 121 and the stator tooth 116a of the stator 112. The driving shaft 120 is rotatably supported by the two bearings 118a and 118b.